Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$98.80	6.343%	$105.0669	$105.07	$105.05	$105.10
Purchase #2	$152.66	4.352%	$159.3038	$159.30	$159.30	$159.30
Purchase #3	$37.46	13.361%	$42.465	$42.47	$42.45	$42.50
Purchase #4	$248.39	4.669%	$259.9873	$259.99	$260.00	$260.00
Purchase #5	$151.40	7.288%	$162.434	$162.43	$162.45	$162.40
Purchase #6	$121.68	5.675%	$128.5853	$128.59	$128.60	$128.60
Purchase #7	$38.31	5.794%	$40.5297	$40.53	$40.55	$40.50
7 purchase totals =	$848.70		$898.3720	$898.38	$898.40	$898.40